Accession Number:

ADA242261

Title:

Computational Studies of the Flow Start-Up Process in Two-Dimensional Unsteady Divergent Nozzles

Descriptive Note:

Final rept. May 90-May 91,

Corporate Author:

ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s):

Report Date:

1991-09-01

Pagination or Media Count:

106.0

Abstract:

A two-dimensional computational study of flow patterns that develop in unsteady overexpanded divergent nozzles with comparison to experimental data was performed and analyzed for two nozzle angles 16 deg and 45 deg. The computations were performed on a Cray XMP48 supercomputer by discretizing the governing equations with an upwind, total variation diminishing TVD, finite- volume, implicit scheme. Experimental shadowgraphs indicated viscous effects were present. Therefore, a systematic study was performed. First, the Euler equations were cast as the governing equations. The Euler equations produced computational results that compared well to inviscid theory, but did not reproduce experimental results. Next, the thin-shear layer equations were cast as the governing equations. Finally, the Baldwin Lomax turbulence model was added to the computational simulations. The thin-shear layer viscous computations improved the comparison of density contour data to shadowgraph pictures over the inviscid computations for the 16 deg-nozzle configuration. However, the laminar viscous and turbulent computations did not significantly alter the inviscid static overpressure solutions for the 16 deg-nozzle. The thin-shear layer viscous computations also improved the comparison of density contour data to shadowgraph pictures for the 45 deg-nozzle configuration. The 45 deg nozzle results showed that viscous effects alter the recompression shock system such that significantly different contour plots and pressure vs. time histories can result between the inviscid, laminar viscous, and turbulent solutions.

Subject Categories:

  • Explosions
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE